lguest: the host code

This is the code for the "lg.ko" module, which allows lguest guests to
be launched.

[akpm@linux-foundation.org: update for futex-new-private-futexes]
[akpm@linux-foundation.org: build fix]
[jmorris@namei.org: lguest: use hrtimers]
[akpm@linux-foundation.org: x86_64 build fix]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 462 insertions, 0 deletions

diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
new file mode 100644
index 000000000000..ce909ec57499
--- /dev/null
+++ b/drivers/lguest/core.c
@@ -0,0 +1,462 @@
+/* World's simplest hypervisor, to test paravirt_ops and show
+ * unbelievers that virtualization is the future.  Plus, it's fun! */
+#include <linux/module.h>
+#include <linux/stringify.h>
+#include <linux/stddef.h>
+#include <linux/io.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/cpu.h>
+#include <linux/freezer.h>
+#include <asm/paravirt.h>
+#include <asm/desc.h>
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/poll.h>
+#include <asm/highmem.h>
+#include <asm/asm-offsets.h>
+#include <asm/i387.h>
+#include "lg.h"
+
+/* Found in switcher.S */
+extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
+extern unsigned long default_idt_entries[];
+
+/* Every guest maps the core switcher code. */
+#define SHARED_SWITCHER_PAGES \
+        DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE)
+/* Pages for switcher itself, then two pages per cpu */
+#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS)
+
+/* We map at -4M for ease of mapping into the guest (one PTE page). */
+#define SWITCHER_ADDR 0xFFC00000
+
+static struct vm_struct *switcher_vma;
+static struct page **switcher_page;
+
+static int cpu_had_pge;
+static struct {
+        unsigned long offset;
+        unsigned short segment;
+} lguest_entry;
+
+/* This One Big lock protects all inter-guest data structures. */
+DEFINE_MUTEX(lguest_lock);
+static DEFINE_PER_CPU(struct lguest *, last_guest);
+
+/* FIXME: Make dynamic. */
+#define MAX_LGUEST_GUESTS 16
+struct lguest lguests[MAX_LGUEST_GUESTS];
+
+/* Offset from where switcher.S was compiled to where we've copied it */
+static unsigned long switcher_offset(void)
+{
+        return SWITCHER_ADDR - (unsigned long)start_switcher_text;
+}
+
+/* This cpu's struct lguest_pages. */
+static struct lguest_pages *lguest_pages(unsigned int cpu)
+{
+        return &(((struct lguest_pages *)
+                  (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]);
+}
+
+static __init int map_switcher(void)
+{
+        int i, err;
+        struct page **pagep;
+
+        switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
+                                GFP_KERNEL);
+        if (!switcher_page) {
+                err = -ENOMEM;
+                goto out;
+        }
+
+        for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
+                unsigned long addr = get_zeroed_page(GFP_KERNEL);
+                if (!addr) {
+                        err = -ENOMEM;
+                        goto free_some_pages;
+                }
+                switcher_page[i] = virt_to_page(addr);
+        }
+
+        switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
+                                       VM_ALLOC, SWITCHER_ADDR, VMALLOC_END);
+        if (!switcher_vma) {
+                err = -ENOMEM;
+                printk("lguest: could not map switcher pages high\n");
+                goto free_pages;
+        }
+
+        pagep = switcher_page;
+        err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep);
+        if (err) {
+                printk("lguest: map_vm_area failed: %i\n", err);
+                goto free_vma;
+        }
+        memcpy(switcher_vma->addr, start_switcher_text,
+               end_switcher_text - start_switcher_text);
+
+        /* Fix up IDT entries to point into copied text. */
+        for (i = 0; i < IDT_ENTRIES; i++)
+                default_idt_entries[i] += switcher_offset();
+
+        for_each_possible_cpu(i) {
+                struct lguest_pages *pages = lguest_pages(i);
+                struct lguest_ro_state *state = &pages->state;
+
+                /* These fields are static: rest done in copy_in_guest_info */
+                state->host_gdt_desc.size = GDT_SIZE-1;
+                state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
+                store_idt(&state->host_idt_desc);
+                state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
+                state->guest_idt_desc.address = (long)&state->guest_idt;
+                state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
+                state->guest_gdt_desc.address = (long)&state->guest_gdt;
+                state->guest_tss.esp0 = (long)(&pages->regs + 1);
+                state->guest_tss.ss0 = LGUEST_DS;
+                /* No I/O for you! */
+                state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
+                setup_default_gdt_entries(state);
+                setup_default_idt_entries(state, default_idt_entries);
+
+                /* Setup LGUEST segments on all cpus */
+                get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
+                get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
+        }
+
+        /* Initialize entry point into switcher. */
+        lguest_entry.offset = (long)switch_to_guest + switcher_offset();
+        lguest_entry.segment = LGUEST_CS;
+
+        printk(KERN_INFO "lguest: mapped switcher at %p\n",
+               switcher_vma->addr);
+        return 0;
+
+free_vma:
+        vunmap(switcher_vma->addr);
+free_pages:
+        i = TOTAL_SWITCHER_PAGES;
+free_some_pages:
+        for (--i; i >= 0; i--)
+                __free_pages(switcher_page[i], 0);
+        kfree(switcher_page);
+out:
+        return err;
+}
+
+static void unmap_switcher(void)
+{
+        unsigned int i;
+
+        vunmap(switcher_vma->addr);
+        for (i = 0; i < TOTAL_SWITCHER_PAGES; i++)
+                __free_pages(switcher_page[i], 0);
+}
+
+/* IN/OUT insns: enough to get us past boot-time probing. */
+static int emulate_insn(struct lguest *lg)
+{
+        u8 insn;
+        unsigned int insnlen = 0, in = 0, shift = 0;
+        unsigned long physaddr = guest_pa(lg, lg->regs->eip);
+
+        /* This only works for addresses in linear mapping... */
+        if (lg->regs->eip < lg->page_offset)
+                return 0;
+        lgread(lg, &insn, physaddr, 1);
+
+        /* Operand size prefix means it's actually for ax. */
+        if (insn == 0x66) {
+                shift = 16;
+                insnlen = 1;
+                lgread(lg, &insn, physaddr + insnlen, 1);
+        }
+
+        switch (insn & 0xFE) {
+        case 0xE4: /* in     <next byte>,%al */
+                insnlen += 2;
+                in = 1;
+                break;
+        case 0xEC: /* in     (%dx),%al */
+                insnlen += 1;
+                in = 1;
+                break;
+        case 0xE6: /* out    %al,<next byte> */
+                insnlen += 2;
+                break;
+        case 0xEE: /* out    %al,(%dx) */
+                insnlen += 1;
+                break;
+        default:
+                return 0;
+        }
+
+        if (in) {
+                /* Lower bit tells is whether it's a 16 or 32 bit access */
+                if (insn & 0x1)
+                        lg->regs->eax = 0xFFFFFFFF;
+                else
+                        lg->regs->eax |= (0xFFFF << shift);
+        }
+        lg->regs->eip += insnlen;
+        return 1;
+}
+
+int lguest_address_ok(const struct lguest *lg,
+                      unsigned long addr, unsigned long len)
+{
+        return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
+}
+
+/* Just like get_user, but don't let guest access lguest binary. */
+u32 lgread_u32(struct lguest *lg, unsigned long addr)
+{
+        u32 val = 0;
+
+        /* Don't let them access lguest binary */
+        if (!lguest_address_ok(lg, addr, sizeof(val))
+            || get_user(val, (u32 __user *)addr) != 0)
+                kill_guest(lg, "bad read address %#lx", addr);
+        return val;
+}
+
+void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val)
+{
+        if (!lguest_address_ok(lg, addr, sizeof(val))
+            || put_user(val, (u32 __user *)addr) != 0)
+                kill_guest(lg, "bad write address %#lx", addr);
+}
+
+void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
+{
+        if (!lguest_address_ok(lg, addr, bytes)
+            || copy_from_user(b, (void __user *)addr, bytes) != 0) {
+                /* copy_from_user should do this, but as we rely on it... */
+                memset(b, 0, bytes);
+                kill_guest(lg, "bad read address %#lx len %u", addr, bytes);
+        }
+}
+
+void lgwrite(struct lguest *lg, unsigned long addr, const void *b,
+             unsigned bytes)
+{
+        if (!lguest_address_ok(lg, addr, bytes)
+            || copy_to_user((void __user *)addr, b, bytes) != 0)
+                kill_guest(lg, "bad write address %#lx len %u", addr, bytes);
+}
+
+static void set_ts(void)
+{
+        u32 cr0;
+
+        cr0 = read_cr0();
+        if (!(cr0 & 8))
+                write_cr0(cr0|8);
+}
+
+static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages)
+{
+        if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) {
+                __get_cpu_var(last_guest) = lg;
+                lg->last_pages = pages;
+                lg->changed = CHANGED_ALL;
+        }
+
+        /* These are pretty cheap, so we do them unconditionally. */
+        pages->state.host_cr3 = __pa(current->mm->pgd);
+        map_switcher_in_guest(lg, pages);
+        pages->state.guest_tss.esp1 = lg->esp1;
+        pages->state.guest_tss.ss1 = lg->ss1;
+
+        /* Copy direct trap entries. */
+        if (lg->changed & CHANGED_IDT)
+                copy_traps(lg, pages->state.guest_idt, default_idt_entries);
+
+        /* Copy all GDT entries but the TSS. */
+        if (lg->changed & CHANGED_GDT)
+                copy_gdt(lg, pages->state.guest_gdt);
+        /* If only the TLS entries have changed, copy them. */
+        else if (lg->changed & CHANGED_GDT_TLS)
+                copy_gdt_tls(lg, pages->state.guest_gdt);
+
+        lg->changed = 0;
+}
+
+static void run_guest_once(struct lguest *lg, struct lguest_pages *pages)
+{
+        unsigned int clobber;
+
+        copy_in_guest_info(lg, pages);
+
+        /* Put eflags on stack, lcall does rest: suitable for iret return. */
+        asm volatile("pushf; lcall *lguest_entry"
+                     : "=a"(clobber), "=b"(clobber)
+                     : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))
+                     : "memory", "%edx", "%ecx", "%edi", "%esi");
+}
+
+int run_guest(struct lguest *lg, unsigned long __user *user)
+{
+        while (!lg->dead) {
+                unsigned int cr2 = 0; /* Damn gcc */
+
+                /* Hypercalls first: we might have been out to userspace */
+                do_hypercalls(lg);
+                if (lg->dma_is_pending) {
+                        if (put_user(lg->pending_dma, user) ||
+                            put_user(lg->pending_key, user+1))
+                                return -EFAULT;
+                        return sizeof(unsigned long)*2;
+                }
+
+                if (signal_pending(current))
+                        return -ERESTARTSYS;
+
+                /* If Waker set break_out, return to Launcher. */
+                if (lg->break_out)
+                        return -EAGAIN;
+
+                maybe_do_interrupt(lg);
+
+                try_to_freeze();
+
+                if (lg->dead)
+                        break;
+
+                if (lg->halted) {
+                        set_current_state(TASK_INTERRUPTIBLE);
+                        schedule();
+                        continue;
+                }
+
+                local_irq_disable();
+
+                /* Even if *we* don't want FPU trap, guest might... */
+                if (lg->ts)
+                        set_ts();
+
+                /* Don't let Guest do SYSENTER: we can't handle it. */
+                if (boot_cpu_has(X86_FEATURE_SEP))
+                        wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
+
+                run_guest_once(lg, lguest_pages(raw_smp_processor_id()));
+
+                /* Save cr2 now if we page-faulted. */
+                if (lg->regs->trapnum == 14)
+                        cr2 = read_cr2();
+                else if (lg->regs->trapnum == 7)
+                        math_state_restore();
+
+                if (boot_cpu_has(X86_FEATURE_SEP))
+                        wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
+                local_irq_enable();
+
+                switch (lg->regs->trapnum) {
+                case 13: /* We've intercepted a GPF. */
+                        if (lg->regs->errcode == 0) {
+                                if (emulate_insn(lg))
+                                        continue;
+                        }
+                        break;
+                case 14: /* We've intercepted a page fault. */
+                        if (demand_page(lg, cr2, lg->regs->errcode))
+                                continue;
+
+                        /* If lguest_data is NULL, this won't hurt. */
+                        if (put_user(cr2, &lg->lguest_data->cr2))
+                                kill_guest(lg, "Writing cr2");
+                        break;
+                case 7: /* We've intercepted a Device Not Available fault. */
+                        /* If they don't want to know, just absorb it. */
+                        if (!lg->ts)
+                                continue;
+                        break;
+                case 32 ... 255: /* Real interrupt, fall thru */
+                        cond_resched();
+                case LGUEST_TRAP_ENTRY: /* Handled at top of loop */
+                        continue;
+                }
+
+                if (deliver_trap(lg, lg->regs->trapnum))
+                        continue;
+
+                kill_guest(lg, "unhandled trap %li at %#lx (%#lx)",
+                           lg->regs->trapnum, lg->regs->eip,
+                           lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode);
+        }
+        return -ENOENT;
+}
+
+int find_free_guest(void)
+{
+        unsigned int i;
+        for (i = 0; i < MAX_LGUEST_GUESTS; i++)
+                if (!lguests[i].tsk)
+                        return i;
+        return -1;
+}
+
+static void adjust_pge(void *on)
+{
+        if (on)
+                write_cr4(read_cr4() | X86_CR4_PGE);
+        else
+                write_cr4(read_cr4() & ~X86_CR4_PGE);
+}
+
+static int __init init(void)
+{
+        int err;
+
+        if (paravirt_enabled()) {
+                printk("lguest is afraid of %s\n", paravirt_ops.name);
+                return -EPERM;
+        }
+
+        err = map_switcher();
+        if (err)
+                return err;
+
+        err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES);
+        if (err) {
+                unmap_switcher();
+                return err;
+        }
+        lguest_io_init();
+
+        err = lguest_device_init();
+        if (err) {
+                free_pagetables();
+                unmap_switcher();
+                return err;
+        }
+        lock_cpu_hotplug();
+        if (cpu_has_pge) { /* We have a broader idea of "global". */
+                cpu_had_pge = 1;
+                on_each_cpu(adjust_pge, (void *)0, 0, 1);
+                clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
+        }
+        unlock_cpu_hotplug();
+        return 0;
+}
+
+static void __exit fini(void)
+{
+        lguest_device_remove();
+        free_pagetables();
+        unmap_switcher();
+        lock_cpu_hotplug();
+        if (cpu_had_pge) {
+                set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
+                on_each_cpu(adjust_pge, (void *)1, 0, 1);
+        }
+        unlock_cpu_hotplug();
+}
+
+module_init(init);
+module_exit(fini);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");